This study is a secondary analysis of data from the National Survey on Drug Use and Health (NSDUH) 2000 which is a publicly available dataset. The NSDUH includes a national probability sample of adolescents in the United States and it will be used to: 1) describe the epidemiological characteristics of youth (aged 12 to 17 years) who have co-occurring substance abuse and mental health (SA/SA) problems compared to those who have either a substance abuse or mental health problem, 2) examine the relationship between symptoms and receipt of SA/MH services for co-occurring problems compared to those with either SA/MH problems; and 3) to identify barriers to access to SA/MH services for you with SA/MH or co-occurring problems. Given that the majority of adolescents with SA/MH health problems do not receive treatment and that this is an under-studied area, this research proposal should make a contribution to understanding why this adolescent SA/MH health services treatment gap exists and may inform how to develop interventions and policies aimed at increasing the number of adolescents receiving services. The research proposal will set the stage for the applicant's long-term goal of becoming a leading expert in the area of youth substance abuse health services research.